There is growing evidence that non-nicotine factors, such as sensory stimuli associated with smoking, may contribute to the maintenance and relapse of smoking. In animal models, the mere presence of a visual stimulus during nicotine delivery increases self-administration. Several interpretations of the effects of nicotine on responding for non-nicotine stimuli are that nicotine: 1) enhances responding maintained by conditioned reinforcers, 2) enhances responding maintained by various environmental consequences (e.g. food, lights), and 3) causes increased activation of existing responses. Unfortunately, self-administration procedures confound responses that produce nicotine with responses that produce conditioned reinforcers. The present study will disentangle the interpretations listed above, while separating the direct effects of nicotine from responses maintained by conditioned reinforcers, using the observing response procedure. This procedure will allow us to compare effects of nicotine on several responses in rats (e.g. resulting in food, lights, extinction) and has built in controls for identifying general increases in already existing activity. Nicotine has also been shown to enhance resistance of responding maintained by food when food is removed. We will assess the reliability and generality of this finding to responses maintained by conditioned reinforcers. The following proposal consists of 2 experiments. Experiment I will investigate several doses of nicotine on responding maintained by different consequences (e.g., primary and conditioned reinforcers) and resistance of such responding during extinction. Experiment II will seek to distinguish whether these effects are mediated by central or perhipheral mechanisms by blocking nicotine with the antagonists mecamylamine and hexamethonium. This project will compare different hypotheses for the effects of nicotine on responding for non-nicotine stimuli and will further validate an animal model for understanding the effects of nicotine on various environmental consequences. [unreadable] [unreadable]